Interferometric analysis method for the manufacture of nano-scale devices

ABSTRACT

The present invention features a method to determine relative spatial parameters between two coordinate systems, which may be a mold and a region of a substrate in which mold is employed to generate a pattern. The method includes sensing relative alignment between the two coordinate systems at multiple points and determines relative spatial parameters therebetween. The relative spatial parameters include a relative area and a relative shape.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of U.S. patentapplication Ser. No. 11/000,331 entitled “Interferometric Analysis forthe Manufacture of Nano-Scale Devices,” naming inventors Pawan KumarNimmakayala, Tom IL Rafferty, Alireza Aghili, Byung-Jin Choi, Philip D.Schumaker, Daniel A. Babbe and Van N. Truskett, filed Nov. 30, 2004,which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The United States government has a paid-up license in this invention andthe right in limited circumstance to require the patent owner to licenseother on reasonable terms as provided by the terms of N66001-01-1-8964and N66001-02-C-8011 awarded by the Defense Advanced Research ProjectsAgency (DARPA).

BACKGROUND OF THE INVENTION

The field of the invention relates generally to nano-fabrication ofstructures. More particularly, the present invention is directed to asystem that facilitates analysis of multiple patterns in superimpositionsuited for the manufacture of nano-scale devices.

Nano-scale fabrication involves the fabrication of very smallstructures, e.g., having features on the order of one nano-meter ormore. A promising process for use in nano-scale fabrication is known asimprint lithography. Exemplary imprint lithography processes aredescribed in detail in numerous publications, such as United Statespublished patent application 2004-0065976 filed as U.S. patentapplication Ser. No. 10/264,960, entitled “Method and a Mold to ArrangeFeatures on a Substrate to Replicate Features having Minimal DimensionalVariability;” United States published patent application 2004-0065252filed as U.S. patent application Ser. No. 10/264,926, entitled “Methodof Forming a Layer on a Substrate to Facilitate Fabrication of MetrologyStandards;” and United States published patent application 2004-0046271filed as U.S. patent application Ser. No. 10/235,314, entitled “Methodand a Mold to Arrange Features on a Substrate to Replicate Featureshaving Minimal Dimensions Variability;” all of which are assigned to theassignee of the present invention.

Referring to FIG. 1, the basic concept behind imprint lithography isforming a relief pattern on a substrate that may function as, interalia, an etching mask so that a pattern maybe formed into the substratethat corresponds to the relief pattern. A system employed to form therelief pattern includes a stage 10 upon which a substrate 12 issupported. A template 14, having a mold 16 with a patterning surface 18thereon. Patterning surface 18 may be substantially smooth and/or planaror may be patterned so that one or more recesses are formed therein.Template 14 is coupled to an imprint head 20 to facilitate movement oftemplate 14. A fluid dispense system 22 is coupled to be selectivelyplaced in fluid communication with substrate 12 so as to depositpolymeric material 24 thereon. A source 26 of energy 28 is coupled todirect energy 28 along a path 30. Imprint head 20 and stage 10 areconfigured to arrange mold 16 and substrate 12, respectively, to be insuperimposition and is disposed in path 30. Either imprint head 20,stage 10 or both vary a distance between mold 16 and substrate 12 todefine a desired volume therebetween that is filled by polymericmaterial 24. Typically, polymeric material 24 is disposed upon substrate12 before the desired volume is defined between mold 16 and substrate12. However, polymeric material 24 may fill the volume after the desiredvolume has been obtained. After the desired volume is filled withpolymeric material 24, source 26 produces energy 28, which causespolymeric material 24 to solidify and/or cross-link conforming to theshape of the substrate surface 24 and mold surface 18. Control of thisprocess is regulated by processor 32 that is in data communication withstage 10 imprint head 20, fluid dispense system 22, source 26, operatingon a computer readable program stored in memory 34.

To allow energy 28 to impinge upon polymeric material 24, it is desiredthat mold 16 be substantially transparent to the wavelength of energy 28so that the same may propagate therethrough. Additionally, to maximize aflux of energy propagating through mold 16, energy has a sufficientcross-section to cover the entire area of mold 16 with no obstructionsbeing present in path 30.

Referring to FIGS. 1 and 2 often a pattern generated by mold 16 isdisposed upon a substrate 112 in which a preexisting pattern in present.To that end, a primer layer 36 is typically deposited upon patternedfeatures, shown as recesses 38 and protrusions 40, formed into substrate112 to provide a smooth, if not planar, surface 42 upon which to form apatterned imprint layer (not shown) from polymeric material 24 disposedupon surface 42. To that end, mold 16 and substrate 112 includealignment marks, which may include sub-portions of the patternedfeatures. For example, mold 16 may have alignment marks, referred to asmold alignment marks, which are defined by features 44 and 46. Substrate112 may include alignment marks, referred to as substrate alignmentmarks, which are defined by features 48 and 50.

Not obtaining proper alignment between mold 16 and substrate 112 canintroduce errors in that pattern recorded on substrate 112. In addition,to standard alignment errors, magnification/run out errors can createsdistortions in the recorded pattern due, inter alia, to extenuativevariations between mold 16 and region of substrate 112 to be patterned.The magnification/run-out errors occur when a region of substrate 112 inwhich the pattern on mold 16 is to be recorded exceeds the area of thepattern on mold 16. Additionally, magnification/run-out errors occurwhen the region of substrate 112 in which the pattern of mold 16 is tobe recorded has an area smaller than the original pattern. Thedeleterious effects of magnification/run-out errors are exacerbated whenforming multiple patterns in a common region. Additional errors mayoccur were the pattern on mold 16 rotated, about an axis normal tosubstrate 112, with respect to the region on substrate 112 in which thepattern on mold 16 is to be recorded. This is referred to as orientationerror. Additionally, when the shape of the periphery of mold 16 differsfrom the shape of the perimeter of the region on substrate 112 on whichthe pattern is to be recorded also causes distortion. This typicallyoccurs when transversely extending perimeter segments of either mold 16and/or region of substrate 112 are not orthogonal. This is referred toas skew/orthogonality distortions.

To ensure proper alignment between the pattern on substrate 112 with thepattern generated by mold 16 it is desired to ensure proper alignmentbetween the mold and substrate alignment marks. This has typically beenachieved employing the aided eye, e.g., an alignment system 53selectively placed in optical communication with both mold 16 andsubstrate 12, concurrently. Exemplary alignment systems have includedocular microscopes or other imaging systems. Alignment system 53typically obtains information parallel to path 30. Alignment is thenachieved manually by an operator or automatically using a vision system.

A need exists, therefore, to provide improved alignment techniques forimprint lithographic processes.

SUMMARY OF THE INVENTION

The present invention features a method to determine relative spatialparameters between two coordinate systems, which may be a mold and aregion of a substrate in which mold is employed to generate a pattern.The method includes sensing relative alignment between the twocoordinate systems at multiple points and determines relative spatialparameters therebetween. The relative spatial parameters include arelative area and a relative shape. These and other embodiments arediscussed more fully below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of an imprint lithography system inaccordance with the prior art;

FIG. 2 is a cross-sectional view of a patterned substrate having aplurality of layers disposed thereon with a mold in superimpositiontherewith in accordance with the prior art;

FIG. 3 is a block diagram showing an imprint lithography system inaccordance with the present invention;

FIG. 4 is a partial perspective view and partial block diagram showingthe components of an interferometric analysis tool shown in FIG. 3 inaccordance with the present invention, with a template being shown froma top down perspective view;

FIG. 5 is a plan view of the template shown in FIG. 4 in accordance withthe present invention;

FIG. 6 is a plan view showing multiple series of features that may beincluded in alignment mark elements shown in FIG. 5;

FIG. 7 is a detailed view of alignment mark features having a firstpitch that may be associated with one or more of the series of featuresshown in FIG. 6;

FIG. 8 is a detailed view of alignment mark features having a secondpitch that may be associated with one or more of the series of featuresshown in FIG. 6;

FIG. 9 is a plan view showing features that may be included in substratealignment mark elements shown in FIG. 3;

FIG. 10 is a detailed view of alignment mark features associated withone or more of the series of features shown in FIG. 9;

FIG. 11 is a plan view showing an image sensed by one or more ofdetectors shown in FIG. 4 when alignment marks features shown in FIGS. 6and 9 are in superimposition and possess a non-zero offset;

FIG. 12 is a plan view showing an image sensed by one or more ofdetectors shown in FIG. 4 when alignment marks features shown in FIGS. 6and 9 are in superimposition and possess a zero offset;

FIG. 13 is a graphical representation showing the intensity signalproduced by one of the detectors shown in FIG. 4 in response to theimage of FIG. 11;

FIG. 14 is a plan view showing the features of FIG. 9 in accordance withan alternate embodiment, in accordance with the present invention;

FIG. 15 a simplified perspective view of the stage shown in FIG. 3 inaccordance with one embodiment of the present invention;

FIG. 16 is a simplified plan view demonstrating one method of coursealignment adjustment of a detector with respect to a template alignmentmark in accordance with an alternate embodiment of the presentinvention;

FIG. 17 is a plan view showing features that may be included insubstrate alignment mark elements shown in FIG. 3 in accordance with analternate embodiment;

FIG. 18 is a plan view showing multiple series of features that may beincluded in alignment mark elements shown in FIG. 5 in accordance withan alternate embodiment;

FIG. 19 is a plan view showing the alignment mark configurationresulting from the alignment mark elements shown in FIGS. 17 and 18 uponthe same being in superimposition;

FIG. 20 is a plan view showing the alignment mark configuration shown inFIG. 19 in accordance with a first alternate embodiment; and

FIG. 21 is a plan view showing the alignment mark configuration shown inFIG. 19 in accordance with a second alternate embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, the present invention includes an imprintlithography system 50 that has a template 52, retained within a templatestage 54, a substrate 56 supported upon a substrate stage 60 and aninterferometric analysis tool (iMAT™) 62 is in optical communicationwith both template 52 and substrate 56. Also are a polymeric fluiddispensing system and a source of actinic radiation, both of which aretypically included in imprint lithography systems, as discussed withrespect to FIG. 1, but are not shown for clarity. An exemplary templatestage includes a chucking system (not shown) and an actuatorsub-assembly (not shown) coupled to imprint head 20 through a flexuresystem (not shown all of which are described in United States patentpublication number 2005-0270516, filed Nov. 30, 2004 as Ser. No.10/999,898, entitled SYSTEM FOR MAGNIFICATION AND DISTORTION CORRECTIONDURING NANO-SCALE MANUFACTURE, with Anshuman Cherala, Byung-Jin Choi,Pawan Kumar Nimmakayala, Mario J. Meissl and Sidlgata V. Sreenivasanlisted as inventors and is incorporated by reference herein.

iMAT™ 62 is coupled with both stages 54 and 60 to communicate therewithover feedback loop 64 to facilitate proper spatial arrangement betweentwo coordinate systems, one defined by template 52 and one defined bysubstrate 56 to obtain a desired spatial arrangement therebetween. Tothat end, iMAT™ 62 produces data concerning multiple spatial parametersof both template 52 and substrate 56 and determines signals in responsethereto to ensure differences between the spatial parameters are withindesired tolerances. To that end, iMAT™ 62 is coupled to sense one ormore of alignment marks on template 52, referred to as templatealignment marks 65, as well as one or more of the alignment marks onsubstrate 56, referred to as substrate alignment marks 66. iMAT™ 62 candetermine multiple relative spatial parameters of template 52 andsubstrate 56 based upon information obtained from sensing alignmentmarks 65 and 66. The spatial parameters includes misalignmenttherebetween, along X and Y directions, as well as relative sizedifference between substrate 56 and template 52 in the X and Ydirections, referred to as a relative magnification/run out measurement,and relative non-orthogonality of two adjacent transversely extendingedges on either template 52 and/or substrate 56, referred to as a skewmeasurement. Additionally, iMAT™ 62 can determine relative rotationalorientation about the Z direction, which is substantially normal to aplane in which template 52 lies and a surface of substrate 56 facingtemplate 52.

Referring to FIG. 4, iMAT™ 62 includes a plurality of detection systems,shown as 70, 80, 90, 100, 110 and 120, as well as two illuminationsources 94 and 124. Each of detection systems 70, 80, 90, 100, 110 and120 includes a detector, 72, 82, 92, 102, 112 and 122 respectively. Eachof detection systems 70, 80, 100 and 110 includes a source ofillumination, shown as 74, 84, 104, and 114, respectively. Each ofillumination sources 74, 84, 94, 104, 114 and 124 is coupled to impingeenergy, such as light, upon a region of template 52 with which detectors72, 82, 92, 102, 112 and 122, respectively, are in opticalcommunication, i.e., lying within the field of view. Specifically,detector 72 is in optical communication with a region 200 of template 52that comprises alignment marks disposed on a mold 198 through focusingoptics 78 and a half-silvered (50/50) mirror 76.

Illumination source 74 produces optical energy that impinges uponhalf-silvered (50/50) mirror 76 that is then directed along a path p₁ toilluminate region 200. A portion of the optical energy impinging uponregion 200 returns along path p₁, passing through half silvered mirror76 and focused onto detector 72 by focusing optics 78. In a similarfashion, detector 82 is placed in optical communication with region 202with half-silvered (50/50) mirror 86 and focusing optics 88 to senseoptical energy, produced by illumination source 84, returning along pathp₂. Detector 102 is placed in optical communication with region 206 withhalf-silvered (50/50) mirror 106 and focusing optics 108 to senseoptical energy, produced by illumination source 104, returning alongpath p₄. Detector 112 is placed in optical communication with region 212with half-silvered (50/50) mirror 116 and focusing optics 118 to senseoptical energy, produced by illumination source 114, returning alongpath p₇. In this fashion, detection systems 70, 80, 100 and 110 employco-axial illumination and detection. Exemplary systems for use adetectors 72, 82, 102 and 112 are available from Sony, Inc. under modelnumbers XEES50, XEHR58 and XE75.

To ensure that the entire area of mold 198 is exposed to allow actinicradiation to propagate therethrough, none of detectors 72, 82, 92, 102,112 and 122; illuminations sources 74, 84, 94, 104, 114 and 124; andother components of the optical train are in superimposition therewith.To that end, each of paths P₁-P₈ forms an angle with respect to a normalto mold 198 in a range of 2° to 15°. With this configuration each ofdetectors 72, 82, 92, 102, 112 and 122 are arranged to sense desiredwavelengths of radiation propagating from regions 200, 202, 204, 206,212 and 214, respectively, while rejecting substantially all otherwavelengths of other orders. For example, each of detectors 72, 82, 92,102, 112 and 122 are arranged to sense one order (say first order, orhigher orders, diffracted wavelengths of light from regions 200, 202,204, 206, 212 and 214, respectively, while rejecting substantially allother wavelengths of other orders.

Detection systems 90 and 120, however, do not employ co-axialillumination and detection. Rather, illumination sources for detectionssystems 90 and 120 are disposed opposite detectors. For example,illumination source 94 directs energy along path p₆ to impinge uponregion 204. A portion of the energy returning from region 204 propagatesalong path p₃ and is collected by optical train 98, which focuses thesame on detector 92. In a similar fashion, illumination source 124directs energy along path p₅ to impinge upon region 214, with a portionof the energy returning therefrom propagating along path p₈. The energypropagating along path p8 is collected by optical train 128 that focusesthe same on detector 122. These non-coaxial illumination units can beused to capture the images with a faster speed as compared to the otherco-axial illumination units. By illuminating from the oppositedirection, the beam does not pass through or reflect off of the 50/50mirror. Therefore, a higher energy of illumination can reach thedetector. For the purpose of higher speed imaging, it is desired tomaximize the beam intensity reaching the detector. Exemplary detectionsystems are available from Darsa Corporation of Waterloo, Canada asmodel numbers 1M150 and 1M75.

Although six detection systems are shown, 70, 80, 90, 100, 110 and 120are shown, any number of detection systems may be present, dependentupon the spatial parameters of interested. For example, more than sixdetection systems may be employed so that two detection systems may bepositioned to sense information from a common region among regions 200,202, 204, 206, 208, 210, 212 and 214, resulting in eight, ten and twelvedetection systems being present (not shown). It is also possible thateach of detection systems 70, 80, 90, 100, 110 and 120 concurrentlyobtain information from more than one of regions 200, 202, 204, 206,208, 210, 212 and 214. In this manner, a highly redundant set of datacan be gathered by the detectors.

Each of detectors 72, 82, 92, 102, 112, 122 produces a signal, inresponse to the optical energy sensed, which is received by a processor130 in data communication therewith. Processor 130 operates on acomputer readable code stored in memory 132, in data communicationtherewith, to determine relative spatial parameters between twocoordinate systems, such as mold 26 and a region 69 of substrate 56 insuperimposition therewith in which patterning is to occur. The area ofregion 69 is typically coextensive with the area of mold 198.

Referring to FIG. 5 disposed at each corner of mold 198 is a set ofalignment marks, shown as 220, 230, 240 and 250. Each set of alignmentmarks includes an template alignment mark element (TAME) that consistsof a plurality of parallel lines spaced apart along a direction, withthe direction along which the plurality of lines associated with one ofthe TAMEs are spaced being orthogonal to the direction along which theplurality of lines are spaced that arc associated with the remainingTAME. For example, set 220, includes TAMEs 221 and 222. TAME 221includes a plurality of parallel lines 223 spaced-apart along the Xdirection, defining a pitch 224. TAME 222 includes a plurality ofparallel lines 225 spaced-apart along the Y direction, defining a pitch226. Similarly, lines 233 of TAME 231 are spaced-apart along the Xdirection as are lines 243 of TAME 241 and lines 253 of TAME 251. Lines235 of TAME 232 are spaced apart along the Y direction, as are lines 245of TAME 242 and lines 255 of TAME 252.

Referring to both FIGS. 4 and 5, each TAME 221, 222, 231, 232, 241, 242,251 and 252 are uniquely associated with one of regions 200, 202, 204,206, 208, 210, 212 and 214. Specifically, the spacing between adjacentalignment marks associated with one of the pairs of alignment mark pairs220, 230, 240 and 250 is established so as to be absent from the regionassociated with the adjacent TAME. For example, the relative dimensionsof each of TAMEs and regions are established so that the entire TAME ispresent with the region. As a result, TAME 221 is associated with region200, TAME 222 is associated with region 202, TAMEs 232 and 231 areassociated with regions 204 and 206, respectively. TAMEs 241 and 242 areassociated with regions 208 and 210 respectively; and TAMEs 252 and 251are associated with regions 212 and 214, respectively. Hiatuses 260 and267, however, are established so that TAME 221 lays outside of bothregions 214 and 202, and both TAMEs 251 and 222 lie outside of region200. As a result, minimized is the amount of energy returning fromoutside of region 200, such as regions 202 and 214 and the distantregions 204, 206, 208, 210 and 212, that is sensed by detector 72. Forthe same reasons, hiatuses 261 and 262 are established so that TAME 232lays outside of both regions 202 and 206, and both TAMEs 231 and 222 lieoutside of region 204. Hiatuses 263 and 264 are established so that TAME241 lays outside of both regions 206 and 210, and both TAMEs 231 and 242lie outside of region 208. Hiatuses 265 and 266 are established so thatTAME 252 lays outside of regions 210 and 214, and both TAMEs 242 and 251lie outside of region 212.

Referring to both FIGS. 5 and 6, although each of TAMEs 221, 222, 231,232, 241, 242, 251 and 252 comprise a single set of parallel lines, eachmay comprise of any number of sets of parallel lines, e.g., 1−n setswhere n is an integer number. As a result one or more of TAMEs 221, 222,231, 232, 241, 242, 251 and 252 may comprise of multiple sets ofparallel lines. In the present embodiment, TAMEs 221, 222, 231, 232, 251and 252 each includes three sets of parallel lines, shown as 270, 271and 272 in abutting relationship so that the spacing therebetween inminimized. The spacing, or pitch, between adjacent pairs of parallellines is substantially constant over the length of the sets 270, 272 and274, with set 270 extending a length between opposed termini 273 and274, set 271 extending a length between opposed termini 275 and 276; andset 272 extending a length between opposed termini 277 and 278. Althoughsets 270, 271 and 272 are shown extending coextensive with one another,this is not necessary.

Referring to FIGS. 6, 7 and 8, the pitch, measured along direction D₁,associated with one of sets 270, 271 and 272 differs from the pitchassociated with the remaining sets 270, 271 and 272. In the presentexample, the pitch associated with sets 270 and 272 match, with thepitch associated with set 271 differing from the pitch associated withsets 270 and 272. For example, sets 270 and 272 each has 41 parallelslines with a width 280 approximately 1 micron wide, measured alongdirection D₁. Adjacent lines are separated by a hiatus 282 ofapproximately 1 micron, measured along direction D₁, resulting in sets270 and 272 having 40 hiatuses providing a pitch of 2 microns. Set 271has 39 parallels lines with a width 284 approximately 1.025 micron wide,measured along direction D₁. Adjacent lines are separated by a hiatus286, measured along direction D₁, of approximately 1.025 micron,resulting in set 271 having 40 hiatuses providing a pitch of 2.05microns. A length of lines, measured along direction D₂, isapproximately 45 microns.

Referring to FIGS. 3, 6 and 9, to determine relative spatial parametersbetween mold 198 and region 69, alignment marks 66 includes a pluralityof alignment mark elements, referred to substrate alignment markelements (SAME) 166. At least one of SAMEs 166 are in superimpositionwith one of TAMEs 221, 222, 231, 232, 241, 242, 251 and 252 and extendsubstantially coextensive therewith. In the present embodiment each ofthe TAMEs, 221, 222, 231, 232, 241, 242, 251 and 252 are insuperimposition with one of the plurality of SAMEs 166. Specifically,each TAMEs 221, 222, 231, 232, 241, 242, 251 and 252 in superimpositionwith one of the SAME 166, differs from the TAMEs 221, 222, 231, 232,241, 242, 251 and 252 in superimposition with the remaining SAMEs 166.

Referring to FIGS. 4, 6, 9 and 10, an exemplary SAME 166 may comprise asingle set of spaced-apart parallel lines, as discussed above withrespect to TAMEs 221, 222, 231, 232, 241, 242, 251 and 252. It isdesired, however, to collect first order diffraction wavelength at anangle oblique to the normal to mold 198, propagating along one of pathsP₁-P₄ and P₇-P₈. To that end, a pattern is employed that is periodic intwo orthogonal directions. Referred to as a checkerboard pattern.Moreover, it is desired to employ three sets of checkerboard patterns,shown as 370, 371 and 372. The three sets of checkerboard patterns 370,371 and 372 are in abutting relationship so that the spacingtherebetween in minimized. Each checkerboard pattern includes aplurality of features 373 each of which is in general rectangular inshape. Each pair of adjacent features is separated by a hiatus 374. Thespacing, or pitch, between adjacent pairs of features 373, alongdirection D₁, in sets 370 and 372 is substantially identical to thepitch of set 271. The spacing, or pitch, between adjacent pairs offeatures 373, along direction D₂, in sets 371 is substantially identicalto the pitch of sets 270 and 272.

To facilitate sensing of wavelengths propagating along a path that isangled obliquely with respect to zero order specularly reflectedwavelengths, the oblique angle selected is dependent upon the geometryof SAME 166, as well as TAMEs 221, 222, 231, 232, 241, 242, 251 and 252and the order of diffraction wavelengths sensed. For example, firstorder diffraction wavelengths at an oblique angle, e.g., in a range of2° to 15° with respect to a normal to mold 198 in order to obtaininformation substantially independent of a distance between mold 198 andregion 69. To that end, the pitch of pairs of adjacent features 373,measured along direction D₂, is approximately 2.2 microns. With thisconfiguration, placement of one of TAMEs 221, 222, 231, 232, 241, 242,251 and 252 in superimposition with substrate alignment mark 166 resultsin set 270 being in superimposition with set 370 and extendingcoextensive therewith; set 271 is in superimposition with set 371,extending coextensive; and set 272 is in superimposition with set 372,extending coextensive therewith. Typical dimensions for TAMEs and SAMEsmay be as high as 400 microns along the direction D₁ and 150 to 250microns along the direction D₂, i.e., each of the parallel lines are 150to 250 microns in length. They may be significantly lower in dimension,for example 100 micron along D₁ direction and 40 micron in length.Alternatively, the dimension along D₁ may be higher (˜1 mm) and D₂ maybe lower (˜40 microns).

Referring to FIGS. 4, 6, 9 and 11, upon being placed in superimpositionwith a SAME 166, the direction D₁ extends parallel to the X-directionfor TAMEs 221, 231, 241 and 251, as well as the SAME 166 insuperimposition therewith. The direction D₁ extends parallel to theY-direction for TAMEs 222,232,242 and 252 and the SAME insuperimposition therewith. In this manner, light impinging upon eachTAME 221, 222, 231, 232, 241, 242, 251 diffracts causing the first orderdiffraction wavelengths to be sensed by one of detector 72, 82, 92, 102,112 and 122 in optical communication therewith. For example lightdiffracted from TAME 221 is sensed by detector 72, light diffracted fromTAME 222 is sensed by detector 82; light diffracted from TAME 232 issensed by detector 92; light diffracted by TAME 231 is sensed bydetector 102; light diffracted by TAME 251 is sensed by detector 122;and light diffracted by TAME 252 is sensed by detector 112. Typically,alignment occurs in the present of polymeric material that substantiallyfills the volume defined between mold 198 and region 69, referred to asin contact liquid align. To that end, it is desired that polymericmaterial not be disposed between and one of TAMEs 221, 222, 231, 232,241, 242, 251 and the SAME 166 in superimposition therewith. To thatend, it may be desired to employ as template 52, the template disclosedin U.S. patent application Ser. No. 10/917,761, filed Aug. 13, 2004,Moat System For An Imprint Lithography Template, which is assigned toassignee of the present invention and is incorporated by referenceherein.

Upon sensing the first order diffraction light, each of detectors 72,82, 92, 102, 112 and 122 obtains an image 469, shown in FIG. 11, ofthree series of spatial varying light intensities 470, 471 and 472 inwhich a adjacent high intensity regions 473 are separated a distance, d,by a low intensity region 474. Series 470 corresponds to diffractivelight generated by the superimposition of sets 270 and 370. Similarlyseries 471 corresponds to superimposition of sets 271 and 371, andseries 472 corresponds to superimposition of sets 272 and 372. A desiredspatial arrangement between region 69 and mold 198 is present upon highintensity regions 473 among series 470, 471 and 472 being positioned togenerate a specific off-set corresponding to the template and substraterelative geometric information, which may be desired or may simplyindicate misalignment.

Referring to FIGS. 4, 11 and 12, in response to sensing images, such asimages 469 and 475, each of detectors 72, 82, 92, 102, 112 and 122produces a signal that is received by processor 130. As a result, sixsignals are received by processor 130. The following discuss, howeverdescribed the process with respect to one of the signals generated bydetectors 72, 82, 92, 102, 112 and 122 for clarity, with theunderstanding that the process occurs on each signal produced by theremaining detectors 72, 82, 92, 102, 112 and 122. The signal includesall of the information captured by detectors 72, 82, 92, 102, 112 and122, i.e., information in the field of view. The field of view of eachof detectors 72, 82, 92, 102, 112 and 122 is approximately 758 microns,measured along 477, by 500 microns, measured along 480. A program storedin memory 132 is operated on by processor 130 to identify a region ofinterest 478 that is a sub-portion of the field of view in whichsubstantially all information other than that concerning sets 470, 471and 472 is omitted. To that end, the region of interest (ROI) isestablished to be an even multiple of pixels along both directions: 695pixels along 479 and 192 pixels along 480. As a result, the dimensionsof ROI 478 is a function of the dimensions associated with TAMEs 221,222, 231, 232, 241, 242, 251 and 252 and TAME 166.

The size of series 470, 471 and 472 corresponds to the size of TAMEs221, 222, 231, 232, 241, 242, 251 and 252, which is equal to the size ofTAME 166. The dimensions of the ROI 478 is established by dividing thewidth and height associated with SAME 166 and TAMEs 221, 222, 231, 231,241, 242, 251 and 252 by the size of the pixels of detectors 72, 82, 92,102, 112 and 122. Additionally, the dimension of ROI 478 along direction480 is selected so as to be an even multiple of the number of series470, 471 and 472, which in the present example is three.

Each of the pixels may have a value associated therewith ranging from0-255. The pixel values are mapped into memory 132 at locations referredto as a memory space. As a result, for each series 470, 471 and 472 ismapped into the memory space as an array having values, from 0 to 255arranged in 695 columns and 64 rows. Thus, memory 132 has three arraysof values mapped therein corresponding to the image sensed by detectors72, 82, 92, 102, 112 and 122.

For each of the three arrays mapped into memory space, a one-dimensionalarray of 695 values is generated. This is accomplished by obtaining, foreach of the 695 columns, an average value for the values associated withthe 64 rows. This corresponds to a substantially three sinusoidalrepresentations of the information 481, 482 and 483 obtained from series470, 471 and 472, respectively. Each of the sinusoids are treated as atime varying signal and are mapped into the frequency domain employing aFast Fourier Transform (FFT) or a Discrete Fourier Transform (DFT) beingwindowed between addresses corresponding to pixels 0-694. Thereafter,the information in the bin associated with the whole number of periodspresent in the ROI is analyzed. The ATAN2 function of the values in theaforementioned bins is determined to find the phase value φ₁, φ₂, and φ₃associated with each sinusoidal signal 481, 482 and 483, respectively.The phase values φ₁, φ₂, and φ₃, having a value of −π to π, aredetermined with respect to the origin of the region of interest 478,i.e., where the region of interest 478 commences.

A difference in phase values between sinusoids 481, 482 and 483 isdetermined as follows:Δ₁=φ₁−φ₂;  1)Δ₂=φ₃−φ₂.  2)Although only one of equations 1 and 2 need be solved, the resolution ofthe phase difference measurements is doubled by obtaining twodifferential phase measurements. To attenuate, if not vitiate, errorattributable to the detectors 72, 82, 92, 102, 112 and 122, an averageof the differences determined in equations 1 and 2 is determined asfollows:(Δ₁−Δ₂)/2=Δ₃.  3)Then the absolute phase difference, Δ₄, between sinusoids 418, 482 and483 is obtained as follows:Δ₃/2=Δ₄  4)

From equation 4) the corresponding linear displacement, D, betweentemplate 56 and mold 198 may be determined from phase Δ₄ as follows:D=P ₁ P ₂Δ₄/4π(P ₁ −P ₂)  5)P₁ is the pitch associated with SAME 371, along direction D₁, and TAMEs270 and 272, and P₂ is the pitch associated with TAME 271 and SAMEs 370and 372. In this manner, detectors 72, 82, 92, 102, 112 and 122facilitate obtaining information concerning six different displacementmeasurements between region 69 and mold 198, i.e., one measurement fromeach of regions 200, 202, 204, 206, 212 and 214. From these sixdisplacement measurements, various relative spatial parametersconcerning mold 198 and region 69 may be determined as discussed byArmitage, Jr. et al. in Analysis of Overlay Distortion Patterns, SPIEVol. 921, pp. 208-222 (1988), which is incorporated by reference herein.Exemplary spatial parameters are linear misalignment along twoorthogonal directions, e.g., the X and Y-directions, rotationalmisalignment along a third direction extending orthogonal thereto, e.g.,the Z-direction. Differences in area, referred to as magnificationdifferences and difference in orthogonality between the perimeter ofmold 198 and region 69. The spatial parameters are ascertained as afunction of the relation between the ideal location of TAMEs 221, 223,231, 233, 241, 243, 251 and 253 with respect to the features on mold 198in reference to the detailed template placement data present in thetemplate design that is typically information defining the placement offeatures on template and, therefore, mold 198, used when fabricating thetemplate. To that end, information concerning the template placementdata is stored in memory 132 to be operated on by processor 130. Fromthe template placement data, the relative spatial parameters may beobtained, using a least squared solution, for the following equations:X _(s) =X ₀ +S _(x) X _(w) cos(θ)+S _(y) Y _(w) sin(θ)+Y _(w) sin(φ)  6)Y _(s) =Y ₀ −S _(x) X _(w) sin(θ)+S _(y) Y _(w) cos(θ)+X _(w) sin(φ)  7)where X_(s) is the measured displacement, D, along the X-direction asdetermined from equation 5 and summed with the X_(w). The known quantityX_(w) is the ideal location along the X-direction of the TAME ofinterest with respect to features of mold 198. Similarly, known quantityY_(w) is the ideal location along the Y-direction of the TAME ofinterest with respect to features of mold 198. Therefore, Y_(s) is themeasured displacement, D, along the Y-direction as determined fromequation 5 and summed with the Y_(w). The variable X₀ is the offsetbetween mold 198 and region 69 along the X-direction. Similarly, thevariable Y₀ is the offset between mold 198 and region 69 along theY-direction. Variables S_(x) and S_(y) are the differences in betweenmold 198 and region 69 along the X and Y-directions, respectively. Thevariable θ is the difference in rotational position between mold 198 andregion 69 about the Z-direction. The variable φ is the difference inorthogonality between the perimeter of mold 198 and the perimeter ofregion 69. As a result, magnification/run out parameters andorthogonality parameters may be determined substantially independent ofthe distance between mold 198 and region 69, i.e., solely from X-Ydisplacement parameters.

Specifically, upon determining the relative spatial parameters betweenmold 198 and region 69, processor 130 generates control signals toregulate the operation of stages 54 and 60 so that desired registrationbetween mold 198 and region 69 is achieved. Registration is demonstratedby detectors 72, 82, 92, 102, 112 and 122 sensing images 469 or 475shown in FIG. 11 as having a desired offset and FIG. 12 as having nooffset, at each or regions 200, 202, 204, 206, 212 and 214. In a typicalalignment process the measurements discussed above are taken as thedistance between mold 198 and region 69 varies, e.g. becoming closer inproximity along the Z-direction. For example, the measurements andcontrol signals may be generated when mold 198 and region 69 arespaced-apart a distance of 4 microns, 1 micron or a final distance inwhich a volume is defined therebetween that is substantially filled withpolymeric material. As a result, the spatial parameters may bedetermined and control signals generated in real time during theimprinting process so as to minimize relative spatial parameters betweenmold 198 and region that are undesirable.

During curing of imprinting material by hardening or cross-linking, thevery photons that are needed for curing may also cause heating of mold198 and region 69. If the intensity of curing light is maintainedreasonably uniform, mold 198 and region 69 may heat up uniformly. Thedifferential heating and/or the differential CTE can cause alignmentmismatches during exposure up to the point where the imprinting materialhas not jelled to behave like a solid that adheres to the substrate.However, the average misalignment may either be estimated by simulationsor by using the alignment measurement systems described here, and thesize of the mold 198 or region 69 can be pre-corrected in such a waythat a desired scaling (magnification) mismatch is achieved using theiMAT 62 just prior to curing. It is desirable that the wavelengths usedfor alignment metrology need to be substantially different from thecuring light.

Based upon the foregoing implementation of Fourier analysis to determinethe phase of sinusoids 481, 482 and 483, it becomes apparent that theaccuracy of these measurements is dependent, in part, upon the properdetermining of the ROI 478. This is to ensure that all informationconcerning series is obtained 470, 471 and 472 are obtained. To thatend, it is desired that ROI 478 be established to within apixel-distance of a corresponding reference point of a referencecoordinate system. In the present example, the reference coordinatesystem is mold 198, but it should be understood that the referencecoordinate system may be region 69. As a result, in the present example,the ROI 478 is established to be within a pixel-distance of thecorresponding reference point on mold 198. This ensures properregistration of ROI 478 with respect to series 470, 471 and 472.

Desired registration of ROI 478, however, is problematic. This is due tothe collection optics associated with each of detectors 72, 82, 92, 102,112 and 122 being configured to collect first order diffractedwavelengths from regions 200, 202, 204, 206, 212 and 214 propagatingalong a path that forms an oblique with respect to a normal to mold 198.As a result, light impinging upon regions 200, 202, 204, 206, 212 and214, from sources 74, 84, 94, 104, 114 and 124, respectively, willresult in very little information corresponding to TAMEs 221, 222, 231,232, 241, 242, 251 and 252, respectively, absent SAME 166 being insuperimposition therewith. Furthermore, proper positioning of a SAME 166in superimposition with one of TAMEs 221, 222, 231, 232, 241, 242, 251and 252 in the absence of proper registration of regions 200, 202, 204,206, 212 and 204 with TAMEs 221, 222, 231, 232, 241, 242, 251 and 252 isproblematic. One manner to overcome this difficulty is to implement atwo step registration process to obtain accurate positioning of regionof interest 478. During the first stage course alignment is achieved towithin a few pixel sizes of resolution. Specifically, the coursealignment scheme should allows the positioning of mold 198 relative toregion 69 wafer to within one period 481, 482 and 483. An off-axisimaging system having a high numerical aperture that is linked to iMAT62 by structural support having a low CTE (example invar or Zerodurmaterials) is desirable. Also appropriately strong mounts are desired sothat the relative location between iMAT 62 and an off-axis camera (notshown) is minimally affected by vibrations. In the present embodiment,the course alignment is achieved by including, on mold 198 a pluralityof groups 500-507 of spaced-apart parallel lines defining gratingshaving a pitch measured orthogonally to the pitch of sets 270, 271 and272.

Groups 500 and 507 are configured in a shape of an arrow, with the pointof group 500 being proximate to a corner of series 270 and the point ofgroup 507 being proximate to a corner of series 272, disposed on a sidethereon opposite to group 500. Spaced apart evenly along theD₁-direction are groups 501-506, each of which are configured in atriangular shape. The apex of each of groups 501, 503 and 505 arepositioned proximate to and faces series 270. The apex of each of groups502, 504 and 506 is positioned proximate to and faces series 272. Thespaced-apart and parallel lines associated with groups 500-507 providewith the requisite pitch and dimensions to facilitate sensing bydetectors 72, 82, 92, 102, 112 and 122. Pitches of groups 500-507 may bethe same as that of the checkered board so that the 1^(st) order, orhigher order if so desired, diffracted wavelengths can be collected andsensed by a detector.

Referring to FIGS. 5, 10, 14 and 15, the configuration of groups 500-507permits locating the ROI 478 to sufficient to enable phase computation,as discussed above. Thereafter, fine alignment occurs by obtaining theabsolute phase difference, Δ₄, discussed above, to properly register thefield of view with the detectors 72, 82, 92, 102, 112 and 122. To thatend, an oversized checkerboard pattern (OCP) 600 is disposed to be insuperimposition with mold 198 and may include sets 370, 371 and 372 eachif which has features 373 separated by a hiatus 374. The dimensions ofany one of sets 370, 371 and 372 may be established to be substantiallylarger in area than mold 198 area. In this manner, relaxed may be thealignment tolerances to place and one of sets 370, 371 and 372 of OCP600 in superimposition with one or more of TAMEs 221, 222, 231, 232,241, 242, 251 and 252. To that end, any one of sets 370, 371 and 372 ofOCP 600 may be sufficiently larger so as to be concurrently insuperimposition with each of TAMEs 221, 222, 231, 232, 241, 242, 251 and252 or any subset thereof. With this configuration OCP 600 may be movedalong X and Y axes and rotated about Z-axis to be placed insuperimposition with one or more TAMEs 221, 222, 231, 232, 241, 242, 251and 252 and in proper orientation therewith to produce the first orderdiffraction wavelengths desired to achieve proper registration.Alternatively OCP 600 may include only one of sets 370, 371 and 372. Inthis fashion, OCP 600 may be coextensive with the area of substrate 56and placed in region 601 of stage 60 upon which substrate 56 issupported. In this fashion, OCP 600 is merely rotated about Z-axis tofacilitate the first order diffraction sensed by detectors to measureproper registration. Alternatively, OCP 600 may be disposed on a region602 of stage 60, outside of region 601. With this configuration OCP 600may be moved along X and Y axes and rotated about Z-axis to be placed insuperimposition with one or more TAMEs 221, 222, 231, 232, 241, 242, 251and 252 and in proper orientation therewith to produce the first orderdiffraction wavelengths desired to achieve proper registration.

Referring to FIGS. 4, 5 and 16, in an alternative embodiment, properregistration of region of interest 478 may be achieved while omittingplurality of groups 500-507. Specifically, as opposed to first orderdiffraction wavelengths, the present example employs sensing, bydetectors 72, 82, 92, 102, 112 and 122, of specularly reflected light.Time present method is discussed with respect to detector 72, butapplies equally to the remaining detectors of the plurality of detectors72, 82, 92, 102, 112 and 122. An illumination source 800 is moved untilone of detectors 72, 82, 92, 102, 112 and 122 receives a substantialchange in flux of light. To that end, it is desired that region 601 bereflective of the illumination generated by source 800. Upon sensing ofthe desired flux of energy, the relative positions of detector 72 andsource 800 are locked so that both move in synchronization over area ofmold 198 to illuminate and sense one of TAMEs 221, 223, 231, 233, 241,243, 251, 233, in this case TAME 221. Thereafter, the position ofdetector 72 is fixed with respect to TAME 221 and source 800 is moved toa position so that one of the remaining detectors, e.g., detectors 82,92, 102, 112 mid 122 sense a substantial change in flux of light.

Referring to FIGS. 5, 6, 17 and 18, SAME 166 and TAMEs 221, 223, 231,233, 241, 243, 251, 253 may comprise of any number of designs foralignment marks. For example, SAME 766 may include two pairs ofspaced-apart gratings elements 767, 768, 769 and 770. As shown gratingelements 767 and 769 are coextensive in area, in superimposition withone another along direction D₂ and spaced apart from each other alongdirection D₁. Each of grating elements 767 and 769 and each includes aseries parallel lines, spaced-apart along direction D₂. Grating elements768 and 770 are coextensive in area, in superimposition with one anotheralong direction D₁ and spaced apart from each other along direction D₂.Each of gratings 768 and 770 includes a series parallel lines,spaced-apart along direction D₁. One or more of TAMEs 221, 223, 231,233, 241, 243, 251, 253, on the other hand, would include two pairs 866of spaced-apart gratings elements 867, 868, 869 and 870. As showngrating elements 867 and 869 are coextensive in area, in superimpositionwith one another along direction D₂ and spaced apart from each otheralong direction D₁, a distance that is less than the distance thatgratings 767 and 769 are spaced-apart. Each of grating elements 867 and869 and each includes a series parallel lines, spaced-apart alongdirection D₂. Grating elements 868 and 870 are coextensive in area, insuperimposition with one another along direction D₁ and spaced apartfrom each other along direction D₂, a distance that is less than thedistance that gratings 768 and 770 are spaced-apart. Each of gratings868 and 870 includes a series parallel lines, spaced-apart alongdirection D₁. With this configuration two pairs 866 are arranged to liewithin SAME 766 upon proper registration of mold 198 with substrateregion 69, shown as 966 in FIG. 19.

Referring to FIGS. 17, 18 and 20, it should be understood that each ofgratings 766, 767, 768, 769, 868, 867, 869 and 870 may include acheckerboard pattern, as discussed above and shown as gratings 967, 968,969, 970 and 1067, 1068, 1069 and 1070. Finally, as shown in FIG. 21,gratings 967, 968, 969, 970 may be formed so as to be contiguous,thereby defining a box 1166, as may gratings 1067, 1068, 1069 and 1070,defining box 1266.

The alignment schemes presented here may be used in the presence ofoptical elements whose parameters are not precisely known withoutsignificantly compromising the quality of the measured signals. Forexample, the template can be nominally 1 to 10 mm thick and thetolerance on its thickness can be 0.1 mm or higher. In addition, theimprint system may have additional windows through which the alignmenthas to be performed the optical properties of which may vary. Forexample, a 1 mm thick transparent window may be subjected to airpressure causing it to be stressed by varying amounts during thealignment process.

The embodiments of the present invention described above are exemplary.Many changes and modifications may be made to the disclosure recitedabove, while remaining within the scope of the invention. For example,each of the above mentioned alignment mark configurations may be imagedusing zero order signal provided an inclined illumination source isreflected off of the marks to a detector that is inclined at an equalbut opposite angle. Alternatively, these marks may also be created insuch a way that their patterned regions are created from parallel linesto enhance the ability to image their first or higher order diffractionsignal from an inclined detection system. The SAME regions may be hollowbox or cross with a solid box or cross shape for the TAME correspondingthereto, or vice versa, and corresponding target for if the TAME is auniversal alignment target. The SAME targets have solid features if zeroorder imaging is pursued. With inclined illumination, a zero orderimaging can be achieved using an inclined collecting optics. If higherorder imaging is pursued, the targets may be created as a composite ofparallel lines with appropriate orientation as a function of theorientation of the inclined collector optics. Therefore, the scope ofthe invention should not be limited by the above description, butinstead should be determined with reference to the appended claims alongwith their full scope of equivalents.

1. A method to determine relative spatial parameters between twosubstrates in a process of alignment comprising: collecting multiplealignment data from phase information using a moiré based pair ofoverlaying alignment marks, one of the pair disposed on each of the twosubstrates; capturing moiré first order microscope images by diffractedlight from one of the alignment marks, while a normal distance betweenthe pair of alignment marks changes from 100 microns to less than 10 nm,wherein all microscopes used for capturing the first order microscopeimages for the alignment process are positioned outside of a beam pathfrom a UV source focused through a template positioned on one of the twosubstrates; and, determining relative spatial parameters between the twosubstrates using the moiré first order microscope images.
 2. The methodas recited in claim 1 where the two substrates are a template and awafer where the wafer is the substrate disposed under the template. 3.The method as recited in claim 1 where a gap between the two substratesis filled with air or imprinting fluid.
 4. The method as recited inclaim 1 where spatial parameters include alignment, magnification anddistortion parameters.
 5. The method as recited in claim 2, wherein thetemplate is an imprint lithography template for imprinting a pattern ina fluid deposited on one of the substrates that is then cured by the UVsource.
 6. The method as recited in claim 5, wherein the beam path ofthe UV source is directed through the imprint lithography template.
 7. Amethod to determine relative spatial parameters between two substratesin a process of alignment comprising: collecting multiple alignment datafrom phase information using a moiré based pair of overlaying substratealignment marks, one of the pair disposed on each of the two substrates;capturing moiré first order microscope images by diffracted light froman alignment mark on the substrate farther from a microscope capturingthe moiré first order microscope images; controlling each microscope,capturing the first order microscope images, in a closed loop positionfeedback using alignment marks on the substrate containing patterns tobe transferred to the other substrate, wherein a normal distance betweenthe pair of overlapping substrate alignment marks changes from 100microns to less than 10 nm; and determining relative spatial parametersbetween two substrates using the first order microscope images.
 8. Themethod as recited in claim 7 where the two substrates are a template anda wafer where the wafer is the farther substrate.
 9. The method asrecited in claim 7 where a gap between the two substrates is filled withair or imprinting fluid.
 10. The method as recited in claim 7 where therelative spatial parameters include alignment, magnification anddistortion parameters.
 11. The method as recited in claim 8, wherein thetemplate is an imprint lithography template for imprinting a pattern ina fluid deposited on one of the substrates that is then cured by a UVsource.
 12. The method as recited in claim 11, wherein the beam path ofthe UV source is directed through the imprint lithography template.